1. Sprinkle patties with ½ tsp each salt and pepper. Cook patties in a large skillet over medium-high heat 5 minutes per side or until no longer pink. Transfer to a plate; keep warm.
2. Meanwhile, stir together mayonnaise, cilantro, lime juice, garlic powder, cumin, and ¼ tsp each salt and pepper in a small bowl.
3. Top patties with tomato, onion, and prepared sauce. Serve burgers using lettuce leaves as buns.